The present invention relates to a method and a device for driving down casings to undisturbed ground without essentially displacing or spoiling sensible overburden and sensible structures. In the casings piles or the like can be driven down for foundation or anchoring in more solid ground.
Sensible overburden is for instance cultural layers from earlier civilizations that can be found under the ground surface having a thickness of up to 3 m. The cultural layers are a source of knowledge for the archeologist to learn about life and human beings during earlier epoches. The cultural layers are in some countries protected by law and must not be ruined.
Sensible structures are for instance walls of unhewn stone for older buildings, especially while works are going on for reinforcing the fundament or sheet piling in or adjacent to the structures. These works must be carried out very carefully if no permanent damage shall occur.
The main characteristics of the invention are that a drilling device that is operated by compressed air is surrounded by a casing, said drilling device at its lower end being provided with adjustable exhaust channels that direct the major part of the compressed air upwards to lead it away between the drill stem and the casing together with the cuttings. Due to the fact that the exhaust channels are adjustable, the intensity of the part of the compressed air directed downwards toward the drill bit can be adapted to the nature of the material that is penetrated. By jet action said part of the compressed air can be led upwards along the grooves on the side walls of the drill bit. The invention also relates to the design of these grooves having a lower narrow inlet and an upwards continuously increasing area. Said design makes it impossible for the cuttings to stick on their way upwards.